linux-kernel - Re: [RFC v2 1/3] cpufreq: ti-cpufreq: add support for omap34xx and omap36xx

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Date:   Fri, 6 Sep 2019 22:46:49 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Tony Lindgren <tony@...mide.com>
Cc:     Benoît Cousson <bcousson@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Adam Ford <aford173@...il.com>,
        André Roth <neolynx@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pm@...r.kernel.org,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [RFC v2 1/3] cpufreq: ti-cpufreq: add support for omap34xx and omap36xx

Hi,

> Am 06.09.2019 um 05:01 schrieb Viresh Kumar <viresh.kumar@...aro.org>:
> 
> On 05-09-19, 07:32, Tony Lindgren wrote:
>> * H. Nikolaus Schaller <hns@...delico.com> [190904 08:54]:
>>> This adds code and tables to read the silicon revision and
>>> eFuse (speed binned / 720 MHz grade) bits for selecting
>>> opp-v2 table entries.
>>> 
>>> Since these bits are not always part of the syscon register
>>> range (like for am33xx, am43, dra7), we add code to directly
>>> read the register values using ioremap() if syscon access fails.
>> 
>> This is nice :) Seems to work for me based on a quick test
>> on at least omap36xx.
>> 
>> Looks like n900 produces the following though:
>> 
>> core: _opp_supported_by_regulators: OPP minuV: 1270000 maxuV: 1270000, not supported by regulator
>> cpu cpu0: _opp_add: OPP not supported by regulators (550000000)
> 
> That's a DT thing I believe where the voltage doesn't fit what the
> regulator can support.

I can confirm this on BeagleBoard C2:

root@...04:~# dmesg|fgrep -i opp
[    2.347442] core: _opp_supported_by_regulators: OPP minuV: 1270000 maxuV: 1270000, not supported by regulator
[    2.359222] cpu cpu0: _opp_add: OPP not supported by regulators (550000000)
[    2.580993] omap2_set_init_voltage: unable to find boot up OPP for vdd_core
root@...04:~# 

> 
>> But presumably that can be further patched.

Well, the opp-v1 table also has this voltage point:

			/* OMAP343x/OMAP35xx variants OPP1-5 */
			operating-points = <
				/* kHz    uV */
				125000   975000
				250000  1075000
				500000  1200000
				550000  1270000
				600000  1350000
			>;


This is OPP4 which is recommended by OMAP3530 data sheet to be 1.27V +/- 5%

Data sheet of tps65950 says

	• VDD1: 1.2-A, buck DC/DC converter (VOUT = 0.6 V to 1.45 V, in steps of 12.5 mV)

This means 1270 mV is not a "step" and rejected by the twl4030 driver.
Maybe nobody did notice yet because the opp-v1 drivers did not warn...

The closest value to 1.27V is 0.6V + 54 * 12.5mV is 1.275V

So let's also change the OPP4 to 1275000 uV in the opp-v2 table.

BR and thanks,
Nikolaus